System for supplying inert gas

ABSTRACT

The exhaust gases from an internal combustion engine are processed for release to the atmosphere or for delivery to a consuming point, such as a subsurface oil producing formation, by passage through a catalytic converter which reduces or eliminates corrosive, combustible, and other undesirable components of the exhaust. In order to insure the presence in the gases of optimum chemical components for effecting the catalytic reaction, an exhaust analyzer and controller adjusts the supply to the engine of an additive of different BTU value than the main fuel supply.

United States Patent Brooks et al.

[451 Sept. 16, 1975 r SYSTEM FOR SUPPLYING INERT GAS lnventors: WalterG. Brooks, Houston, Tex.;

John P. Knodle, Ventura, Calif.

[73] Assignee:

Production Operators, Inc.,

Houston, Tex.

Filed:

US. Cl.

Int. Cl.

Dec. 26, 1972 Appl. No.: 318,396

BOIJ 7/00; F01N 3/15 Field of Search 23/288 F, 281; 123/121;

60/276, 285; 48/DlG. 8

References Cited UNITED STATES PATENTS 48/D1G. 8 123/121 X Barstow23/281 UX Barlow 23/288 F X Keith et a1. 60/276 X Barstow 60/276 XBurridge 73/116 Urquhart Rockwell 3,696,618 10/1972 Boyd et al. 23/288 FX 3,718,000 2/1973 60/285 3,725,012 4/1973 23/288 F X 3,753,424 8/1973123/121 3,800,768 4/1974 Rhodes et a1. 60/285 X Primary ExaminerJosephScovronek Assistant ExaminerArnold Turk Attorney, Agent, or Firm-DelmarL. Sroufe; Frank B. Pugsley; Larry B. Feldcamp [57] ABSTRACT 5 Claims, 1Drawing Figure SYSTEM FOR SUPPLYING INERT GAS BACKGROUND OF THElNVENTiQN Where the exhaust from an internal combustion engine is to beutilized as an inert gas, for instance, supplied through a compressor toa subsurface oil producing formation, it is necessary torender theexhaust essentially free of corrosive, acid-forming and otherundesirable components. This has been achieved heretofore by installingin the exhaust duct a catalytic converter containing a catalyst such asplatinum or palla-' dium which induces a reduction of the nitrogenoxides and elimination of free oxygen. However, the efficacy of such aconverter depends upon the presence in the exhaust of optimum quantitiesof reducing agents such as carbon monoxide and free hydrogen. The priorart devices for insuring the optimum chemical composition of the exhaustgases for such catalytic conversion have utilized exhaust gas ahalyzerseither to adjust the ratio of fuel and air in the combustible mixturesupplied to the engine, or have supplied an additive, as the fuelitself, directly to the catalytic converter. In the first case, propercontrol of the combustible content of exhaust gases by control of thefuel and air ratio in the mixture supplied to multiple carburetors ormixing valves is not feasible. In the latter case, close control of theexhaust constituents has not been achieved.

Accordingly, it is an object of the present invention to provide asystem for rendering the exhaust gases from an internal combustionengine continuously at the optimum composition for maximum catalyticconversion even where multiple carburetors are used.

Another object is to provide an improved system for insuring closercontrol of the catalytically converted gases in the exhaust system froman internal combustion engine.

SUMMARY OF THE INVENTION In accordance with the present invention theexhaust gases from an internal combustion engine are directed, asheretofore, through a catalytic converter. In order to improve theconverter action, an exhaust gas analyzer is utilized to control the BTUvalue of the fuel supply to the engine, by adding to the intake fuelcontrolled proportions of a gas having a substantially different BTUthan the main fuel gas. Greater BTU additive gas will be used where thefuel gas has an abnormally low BTU value (for example, less than about900 BTU per cu. ft.) and lower BTU additive gas will be used where thefuel gas exceeds normal BTU values (for example, above 1000 BTU per cu.ft.). For intermediate value fuel gas (between about 900 and 1000 BTUper cu. ft.) either higher or lower BTU additive gas may be used with acorresponding adjustment of the carburetor or fuel mixing valves.

In the accompanying drawing, the FIGURE is a schematic representationillustrating an exemplary form of the apparatus.

DETAILED DESCRIPTION OF THE FIGURE An internal combustion engine A,preferably of the reciprocating type, is equipped with carburetion ormixing valve equipment B for properly mixing fuel and air constituentsintroduced through piping 6 and 7 for supply to the firing chambers.Where the apparatus is utilized in the oilfields, the fuel supply may benatural gas which generally is present and available. The exhaust line8leads from the engine exhaust manifold to a conventional catalyticconverter C containing a suitable catalytic agent, such as platinum orpalladium, over which the exhaust is directed for eliminating corrosiveoxides of nitrogen and other undesirable materials. The treated exhaustmay then be supplied through line 10, valve 26, compressor E and line 9to a process or consuming point, such as a water sweetening plant (forremoval of gases such as H 8) or a subsurface oilproducing formation.Alternatively, the inert gas from the converter may be discharged to theatmosphere through line 10 and valve 25.

A portion of the exhaust is bypassed as at 1 1 to an exhaust gasanalyzer D, also of conventional design, for instance, a thermalconductivity type. The exhaust gas analyzer is adapted to respond to thechemical composition of the exhaust gas. Responses from the analyzer,delivered through a pneumatic or electrical line 12, energize theactuator 13 of an automatic valve 14 in a line 15 leading from a sourceof additive gas 16 to the main fuel supply line 6 and thence to theengine carburetion system. Alternatively, the additive gas may beintroduced into the intake manifold downstream of the carburetionsystem.

As another alternative, pneumatic line 12 may control an automatic valve17 in a connection 18, shown dotted, between discharge duct 9 and line15 and thence to the engine intake permitting a portion of the produced,essentially zero BTU inert gas to be used as the additive gas. Manualvalves 19 and 20 are provided in lines 15 and 18. In those embodimentswhere the exhaust is released to the atmosphere, the compressor E willbe employed to raise the exhaust gas pressure only enough to permit flowthrough connection 18 through line 15 to intake line 6.

OPERATION The purpose of the additive supplied, either through line 15,6 or line 18, 15, 6 is to adjust the BTU value of the engine intakemixture so that the components of the exhaust in duct 8 will be optimumfor action of the catalytic converter as explained above. Where fuel gashas an intermediate BTU value (about 900 to 1000 BTU per cu. ft.) alower BTU additive gas may be used and when the fuel gas has a high BTUvalue (above about 1000 BTU per cu. ft.) the additive gas should be aninert gas or a gas with a lower BTU value than that of the main supplygas. With the use of such low BTU or inert additive gas, the carburetoris initially adjusted without the additive gas to provide a rich fuelmixture so as to produce an excess of combustible gases as carbonmonoxide and hydrogen in the exhaust over the amount required forefficient operation of the catalytic converter (about 24%). The amountof excess caarbon monoxide and hydrogen in the exhaust before theintroduction of the additive is not critical but it should besufficiently in excess of the desired amount to be certain that asufficient amount will always be available with normal fluctuations inthe BTU value of the fuel supply.

Inert or low BTU gas additives may be supplied from the additive gassource 16 through manual valve 19 and past the automatic control valve14. In the alternative,

the catalytic converter. When inert gas issupplied to a consuming pointor process, the alternate supply of inert gas may be obtained by openingmanual valve and the inert gas will then be supplied tothe fuel systemthrough automatic control valve 17. Manual valves 19 and will be closedat this time.

When the produced inert gas is used as an alternate supply of fueladditive gas and the remainder of the produced inert gas is dischargedto the atmosphere, manual valves 20 and 25 will be open and valves 19and 27 will be closed. As previously noted, in this case the compressorE will then be employed only to raise the exhaust gas pressuresufficiently to permit flow through line 18, valve 20 andline 15 to theengine intake 6. During such operation automatic control valve 17 willcontrol the supply of the inert gas to the fuel mixture.

Valve 26 is provided to illustrate an embodiment in which compressor Ewould not be used and the entire production of inert gas would bedischarged through manual valve 25 to the atmosphere. Such circumstancewould normally occur when the catalytic converter is used to reduce theundesirable corrosive or combustible components of the exhaust gas fordischarge to the atmosphere and the source 16 is used for the additivegas supply.

Source 16 may be used to store a supply of gas of lesser or greater BTUvalue than the main gas supply. A gas having a greater BTU value thanthat of normally available natural gas would include, for example, anLPG (liquified petroleum gas) such as butane or propane. Such a high BTUgas may be used if the fuel gas has an intermediate BTU value (about900-1000 BTU per cu. ft.) and such greater BTU additive will be used ifthe fuel gas has a relatively low BTU value (below about 900 BTU per cu.ft.). In such case, of course, the carburetor or fuel mixing valve willbe adjusted to a lean mixture as evidenced by a low proportion ofcombustibles in the exhaust gas, normally less than 2 percent, beforethe additive is introduced into the fuel supply. The rich additive gasis then introduced as in the case of the lean additive gas by openingmanual valve 19 and controlling the desired proportion supplied to thecarburetor system by the operation of automatic valve 14.

We have found that the system herein disclosed and claimed insures thesupply of an exceptionally uniform composition of exhaust gases,particularly as to reductants, to the catalytic converter, with theresult that the main fuel gas supply may be controlled as necessary forproper engine operation and also for continuing uniform supply of inertgas to the consuming point. Various features may be modified as willoccur to those skilled in the art, and the exclusive use of allmodifications as come within the scope of the appended claims iscontemplated.

We claim:

1. In an apparatus for the production of an inert gas by the conversionof exhaust gas from an internal combustion engine said apparatus havinga source of hydrocarbon fuel of predetermined BTU value connected tosaid engine by a fuel supply means, and exhaust duct means connected tosaid engine to convey the exhaust gases therefrom; and a catalyticconverter provided in said duct means for reacting the exhaust gasesover a catalyst of the group consisting of platinum and palladium, theimprovement comprising:

a. Exhaust gas analyzing means connected to said duct means between saidengine and said converter to sample and respond to the chemicalcomposition of the exhaust gas;

b. A source of fuel additive of BTU value differing from that of thehydrocarbon fuel;

c. A connection between said latter source of fuel additive and saidfuel supply means;

d. A valve controlling said connection; and

e. An operative connection between said analyzing means and said valvefor adjusting the quantity of fuel additive admixed with saidhydrocarbon fuel supplied to the engine in proportions which willmaintain the combustibles in the exhaust gas at a level sufficient forefficient operation of the catalytic converter.

2. Inert gas generating apparatus as described in claim 1 in which saidsource of fuel additive is adapted to supply to the engine a fueladditive comprising a liquefied petroleum gas of greater BTU value thanthe BTU value of the gas delivered by said fuel supply means.

3. Inert gas generating apparatus as described in claim 1 in which saidsource of fuel additive comprises a communication with said exhaust ductdownstream of the catalytic converter.

4. Inert gas generating apparatus as described in claim 1 wherein acompressor is connected to said exhaust duct downstream from saidconverter, and a discharge conduit is connected to said compressor tocarry said inert gas from said compressor to a consuming point.

5. Inert gas generating apparatus as described in claim 1 wherein adischarge conduit is connected to said catalytic converter to releasesaid inert gas to the atmosphere.

1. IN AN APPARATUS FOR THE PRODUCTION OF AN INERT GAS BY THE CONVERSIONOF EXHAUST GAS FROM AN INTERNL COMBUSTION ENGINE SAID APPARATUS HAVING ASOURCE OF HYDROCARBON FUEL OF PREDETERMINED BTU VALUE CONNECTED TO SAIDENGINE BY A FUEL SUPPLY MEANS, AND EXHAUST DUCT MEANS CONNECTED TO SAIDENGINE TO CONVEY THE EXHAUST GASES THEREFROM, AND A CATALYTIC CONVERTERPROVIDED IN SAID DUCT MEANS FOR REACTING THE EXHAUST GASES OVER ACATALYST OF THE GROUP CONSISTING OF PLATINUM AND PALLADIUM, THEIMPROVEMENT COMPRISING: A. EXHAUST GAS ANALYZING MEANS CONNECTED TO SAIDDUCT MEANS BETWEEN SAID ENGINE AND SAID CONVERTER TO SAMPLE AND RESPONDTO THE CHEMICAL COMPOSITION OF THE EXHAUST GAS, B. A SOURCE OF FUELADDITIVE OF BTU VALUE DIFFERING FROM THAT OF THE HYDROCARBON FUEL, C. ACONNECTION BETWEEN SAID LATTER SOURCE OF FUEL ADDITIVE AND SAID FUELSUPPLY MEANS, D. A VALVE CONTROLLING SAID CONNECTION, AND E. ANOPERATIVE CONNECTION BETWEEN SAID ANALYZING MEANS AND SAID VALVE FORADJUSTING THE QUANTITY OF FUEOL ADDITIVE ADMIXED WITH SAID HYDROCARBONFUEL SUPPLIED TO THE ENGINE IN PROPORTIONS WHICH WILL MAINTAIN THECOMBUSTIBLES
 2. Inert gas generating apparatus as described in claim 1in which said source of fuel additive is adapted to supply to the enginea fuel additive comprising a liquefied petroleum gas of greater BTUvalue than the BTU value of the gas delivered by said fuel supply means.3. Inert gas generating apparatus as described in claim 1 in which saidsource of fuel additive comprises a communication with said exhaust ductdownstream of the catalytic converter.
 4. Inert gas generating apparatusas described in claim 1 wherein a compressor is connected to saidexhaust duct downstream from said converter, and a discharge conduit isconnected to said compressor to carry said inert gas from saidcompressor to a consuming point.
 5. Inert gas generating apparatus asdescribed in claim 1 wherein a discharge conduit is connected to saidcatalytic converter to release said inert gas to the atmosphere.